Commercial foamed back carpet, carpet modules, and carpet tiles are commonly produced by laminating a preformed chemically blown foam of the proper thickness and density to a pre-coated carpet. This is commonly done by heating the pre-coated carpet and the preformed closed cell foam to the hot melt phase of the polyvinyl chloride and pressing the two layers together. Other variations of this method, some of which involve adhesives, are common. Most of these involve heating of the preformed closed cell foam.
Heating of chemically blown closed cell foam always results in the expansion of the closed cells with a corresponding growth in the dimensions of this layer. In the case of tufted and back coated carpet, the thermal expansion of the solid elastomeric back coats the fibrous primary backings into which the carpet yarn is tufted. The thermal expansion of this composite is much less than the expansion of the gas filled cells of the foam layer. In the case of carpet formed by implanting fibers in an elastomeric layer to which the preformed foam layer is subsequently laminated, the same differential expansion and contraction factors occur. This style is referred to as Fusion Bonded Carpet. When an expanded layer is laminated in the presence of heat to another less expanded layer, tension forces develop upon cooling. These forces result in a latent tendency of the product to curl and/or dome. The foam layer wants to pull in under the product. In the case of carpet tiles, the tiles from the center of the composite will dome differently from side to side.
Also in the case of carpet or tiles produced by this method, the relatively smooth under surface of the carpet or tile does not allow substrate moisture or hydrostatic pressure to dissipate, resulting in condensation of the vapors under the carpet or the tile. In addition, it is known that the stabilization of dimensions in such a product requires several reinforcing fleeces or scrims. The processes described do not lend themselves to the incorporation of several fleeces or scrims.
In the existing art, the foam layer is formed by a layer of polyvinyl chloride (PVC) plastisol (dispersion of PVC resin in plasticizer) on an impervious carrier, such as but not limited to, a stainless steel belt or a Teflon.RTM. coated wire or fiberglass belt, and expanding the layer from a density of 70 to 90 pounds per cubic foot down to 15 to 25 pounds per cubic foot. A general formulation for such a foam layer is:
______________________________________ PARTS ______________________________________ PVC resin (K value 62 to 70) 100 Plasticizer (Di Octyl Phthalate) 60 to 100 Nitrogen producing agent (Azo Di Carbonamide) 3 Blow promoter (Zinc Octoate) 1 Filler (Calcium Carbonate) 0 to 150 Color as needed ______________________________________
"K" value is a universal method of indicating the molecular weight of the PVC molecule.
After casting the formulation on the carrier belt, the PVC plastisol is heated until the material reaches 370 to 380.degree. F., converting all the blowing agent to gaseous nitrogen.
According to the present invention the problems with curling or doming that occur in the commercial prior art are substantially eliminated, and the disadvantageous condensation of vapors under the carpet of the tile is also substantially eliminated. The carpet tile or roll that is produced according to the present invention has a backing that is non-slip, so that if desired the carpet tiles or roll may be installed without adhesive, namely with conventional tacking of the carpet roll or tile at the perimeter portions, or utilizing like conventional techniques. The OMFRFL can also be adhered/applied using a thermoplastic material such as polypropylene, polyethylene, or other thermoplastic compound.
According to the invention, an open mesh fiber reinforced foam layer ("OMFRFL") is incorporated onto or with the back of a back coated carpet, or fusion bonded carpet. The stable construction of the finished product is the result of the addition of a scrim in the open mesh foam as well as the open nature of that layer. This fiber mesh reinforcement can be either a second or a third fiber layer. It is a third fiber layer if the open mesh scrim foam is installed after a second layer of fleece of scrim, woven or non-woven, is adhered to the back coated or fusion bonded carpet. The OMFRFL is applied either with a foamed or non-foamed adhesive system that can be solid, frothed, or latex applied and heated to cure or fuse the adhesive. The temperature needed to accomplish this (less than about 310.degree. F.) will not significantly expand the reinforced open mesh foam across the width or in the lengthwise direction of the product any more than the carpet to which it is being bonded. The OMFRFL can also be applied using a thermoplastic hot melt material such as amorphous polypropylene, or polyethylene that is viscous when hot and rubbery when cooled. All the expansion and subsequent contraction of the foam will be in a vertical direction to the plane of the carpet. The resulting foam backed carpet or tile allows air and hydrostatic or gas pressure to dissipate, reducing the trapped vapor's tendency to condense under the carpet, thus conditions for mold and mildew formation are reduced.
According to one aspect of the present invention a method of producing a carpet in tile or roll form using an OMFRFL with foam nodules is provided. The method comprises the steps of: (a) Producing a carpet in tile or roll form having a primary backing through which carpet fiber bundles are tufted and a precoat locking the tufts in place to prevent easy extraction of individual fibers, so that a tufted fiber face and relatively smooth opposite back face are provided. (b) Bringing the open mesh fiber reinforced foam layer with foam nodules into intimate contact with the relatively smooth back face, And (c) substantially permanently adhering the open mesh fiber reinforced foam layer with foam nodules in contact with the relatively smooth back face to provide a carpet tile or roll that has reduced curling or doming and/or that is substantially prevented from curling or doming and may be installed with or without adhesive.
There are two alternative manners in which the method steps (b) and (c) may be carried out. According to one aspect of the method, a preformed back or precoated carpet has a non-fused adhesive system associated therewith, onto which the OMFRFL is formed, with subsequent fusing; or according to another aspect, while the vinyl backing of the carpet roll or tile still has hot melt properties as it emerges from the final fusion oven, the OMFRFL is forced into intimate contact therewith.
That is, according to the first aspect of the method of the invention, step (c) is practiced by applying a non-fused adhesive formulation to the relatively smooth back face, and then after step (b), fusing the adhesive at a temperature low enough (e.g. a maximum fusing temperature of 310.degree. F., preferably a maximum temperature of about 300.degree. F.) to prevent the collapse of the preformed foam nodules of the open mesh fiber reinforced foam layer. Step (c) is further practiced by applying as the adhesive formulation a formulation comprising, or consisting essentially of:
______________________________________ PVC Copolymer 100 parts Plasticizer 50-100 parts Filler 0-200 parts Silicone surfactant 0-4 parts Fumed silica 0-2 parts. ______________________________________
Preferably step (c) is further practiced by applying as the adhesive formulation about 25-150 parts filler, sufficient silicone surfactant to provide a formulation density below 50 pounds per cubic foot, and sufficient fumed silica to provide a formulation Brookfield viscosity of about 30,000-60,000 centipoise at a spindle speed of 2 rpm.
In practice of the second aspect of the method of the invention, step (c) is practiced by practicing step (a) using a fusion oven, and so that the relatively smooth carpet back face has hot melt properties as it emerges from the fusion oven; and step (b) is practiced by forcing the open mesh fiber reinforced foam layer with foam nodules into intimate contact with the relatively smooth back face so that the back face contacts, or at least partially envelops, the foam nodules to provide a substantially instant bond. Step (c) may be further practiced by providing as at least part of the carpet back, contacting the OMFRFL, a formulation comprising (or consisting essentially of):
______________________________________ PVC resin with a K value of 62-75 100 parts Plasticizer 60-100 parts Filler 0-250 parts ______________________________________
and substantially devoid of blowing agent (preferably having no more than trace amounts). There is also the further step of cooling the carpet with OMFRFL with foam nodules backing, which cooling takes place during normal processing.
In both aspects of the method of the invention, step (a) may be further practiced to provide a reinforcing scrim (as is conventional for carpet tiles) as part of the carpet adjacent the relatively smooth back face, the scrim typically being a fleece, woven, or non-woven in construction as is conventional. Also, in both aspects of the method, step (b) may be practiced utilizing rollers which engage the tufted face of the carpet roll or tile, and the face of the OMFRFL opposite the carpet tile or roll, and squeezing them together with pressure that is adjusted depending upon the details of the materials used so that the appropriate intimate contact is reached without squeezing necessary somewhat fluid materials out of the nip area of the rollers. Other conventional equipment aside from the rollers may also be used for this purpose, including converging conveyor belts, relatively low friction surfaces, combinations thereof, or the like.
According to another aspect of the present invention a carpet roll or tile is provided comprising the following components: A primary backing having carpet fiber bundles tufted therethrough, the fibers bundles providing a tufted face. A precoat locking the tufts in place to prevent easy extraction of individual fibers and providing a relatively smooth back face opposite the tufted face. And an open mesh fiber reinforced foam layer with foam nodules held in substantially intimate contact with the relatively smooth back face.
The OMFRFL with foam nodules is preferably held in substantially intimate contact with the relatively smooth back face by a fused adhesive, such as an adhesive having a formulation comprising or consisting essentially of:
______________________________________ PVC Copolymer 100 parts Plasticizer 50-100 parts Filler 0-200 parts ______________________________________
a sufficient amount of silicone surfactant to provide a formulation density below 50 pounds per cubic foot, and PA1 a sufficient amount of fumed silica to provide a formulation pre-fusing Brookfield viscosity of about 30,000-60,000 centipoise at a spindle speed of 2 rpm.
Alternatively, the OMFRFL with foam nodules may be held in substantially intimate contact with the relatively smooth back face by a hot melt formulation of the back face comprising or consisting essentially of:
______________________________________ PVC resin with a K value of 62-75 100 parts Plasticizer 60-100 parts Filler 0-250 parts ______________________________________
and substantially devoid of blowing agent. The hot melt formulation is not limited to PVC, but can also be any thermoplastic material that acts as a flexible layer or adhesive.
The hot melt formulation is not limited to PVC but can also be any thermoplastic material that acts as a flexible layer or adhesive.
According to another aspect of the present invention a carpet tile is provided. The carpet tile is substantially the same as the carpet roll as described above, except that it additionally includes a reinforcing scrim adjacent the relatively smooth back face and held in place at least in part by the precoat. Under some circumstances the carpet roll may also have a reinforcing scrim. Also, according to the invention carpet rolls or tiles may be made by practicing the method steps described above with respect to the method aspect of the invention.
It is a primary object of the present invention to provide a carpet in tile or roll form having at least some of the following advantages; it is substantially prevented from curling or doming, has enhanced antagonistic conditions to mold and mildew formation, and may even be installed without adhesive if desired. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.